[colorful-home] Use QtComponents API and a gconf key to read framebuffer orientation

/desktop/jolla/components/screen_rotation_angle should be set to the
offset in degrees from portrait for the framebuffer's orientation to
ensure switcher items display in the correct orientation.
[colorful-home] Fix window close button for wayland
Merge pull request #17 from special/qt5

[qt5] Use a gconf key to configure framebuffer orientation and fix window close